guzzlehttp/psr7 is a PSR-7 HTTP message library. Versions prior to 1.8.4 and 2.1.1 are vulnerable to improper header parsing. An attacker could sneak in a new line character and pass untrusted values. The issue is patched in 1.8.4 and 2.1.1. There are currently no known workarounds.
{
    "cpes": [
        "cpe:2.3:a:drupal:drupal:*:*:*:*:*:*:*:*"
    ],
    "severity": "High"
}